[RFC] ao_wasapi: add Windows Spatial Audio output

DOCS/interface-changes/wasapi-spatial.txt

@@ -0,0 +1 @@
+add the `wasapi-spatial` Windows audio output

DOCS/man/ao.rst

@@ -304,6 +304,19 @@ Available audio output drivers are:
     (Note: only supports mono, stereo, 4.0, 5.1 and 7.1 channel
     layouts.)
 
+``wasapi-spatial`` (Windows only)
+    Sends decoded PCM channel layouts to the Windows Spatial Audio API as
+    static audio objects. Windows renders the objects through the spatial
+    audio path for the selected output device.
+
+    This driver supports decoded PCM only. It doesn't pass through compressed
+    bitstreams or native object metadata from Dolby Atmos or DTS:X streams.
+    It never requests exclusive audio access.
+
+    The driver isn't selected automatically. Use
+    ``--ao=wasapi-spatial,wasapi`` to try it and fall back to regular WASAPI.
+    Use ``--audio-device=help`` to list available devices.
+
 ``wasapi``
     Audio output to the Windows Audio Session API.
 

audio/out/ao.c

@@ -51,6 +51,7 @@ extern const struct ao_driver audio_out_opensles;
 extern const struct ao_driver audio_out_null;
 extern const struct ao_driver audio_out_alsa;
 extern const struct ao_driver audio_out_wasapi;
+extern const struct ao_driver audio_out_wasapi_spatial;
 extern const struct ao_driver audio_out_pcm;
 extern const struct ao_driver audio_out_lavc;
 extern const struct ao_driver audio_out_sdl;
@@ -105,6 +106,9 @@ static const struct ao_driver * const audio_out_drivers[] = {
     &audio_out_sndio,
 #endif
     &audio_out_null,
+#if HAVE_WASAPI_SPATIAL
+    &audio_out_wasapi_spatial,
+#endif
 #if HAVE_COREAUDIO
     &audio_out_coreaudio_exclusive,
 #endif

audio/out/ao_wasapi.h

@@ -108,6 +108,8 @@ char *mp_PKEY_to_str_buf(char *buf, size_t buf_size, const PROPERTYKEY *pkey);
 void wasapi_list_devs(struct ao *ao, struct ao_device_list *list);
 bstr wasapi_get_specified_device_string(struct ao *ao);
 LPWSTR wasapi_find_deviceID(struct ao *ao);
+bool wasapi_load_device(struct mp_log *l, IMMDevice **ppDevice,
+                        LPWSTR deviceID);
 
 bool wasapi_thread_init(struct ao *ao);
 void wasapi_thread_uninit(struct ao *ao);